I've done the sveral of the Brooks Duo's including Knox. They are typically a much more casual affair than tri's, mor elike the atmosphee of a Sri Chimoy race. There are a lot more beginners than the tri's because of no swimming (well duh

). I haven't entered as a team, but typically there will be a tag point somewhere around the transition area.
6min/kms won't be a problem (that's about me). In the main event that will put you back of the pack, but in the shorter event further up.
If you have time (and maybe you won't with kids) hang about for the spot prizes. Last time I was there they had so many spot prizes almost everyone that hung around got one. A mate and I felt like the only ones that hadn't got anything and when I pointed it out he got a HRM, and all I got were socks.